From ages 19 to 28, Augustine is a teacher of rhetoric and an adherent of Manichaeism, both false occupations. During this time, he lives with a woman and has a child by her. He is faithful to her, although their relationship was based on sex, not on friendship. He despises soothsayers, but he continues to consult astrologers and to practice astrology himself, despite the advice of a wise friend that astrology is phony.
By now, Augustine is an adult, teaching rhetoric back in his hometown of Thagaste. He continues as a Manichee Hearer (also called Auditor), meaning he is a disciple, although not one of the most highly placed in the sect, one of the Elect. He identifies both the public and the private aspects of his life as based on deception. Just as he is deceived by the false words of the Manichees, he teaches his students to deceive others with words in the courts of law. He still has a conscience, however, as he prefers to teach "virtuous" students when he can find them, and he tries to impress his students with the idea that it is better to let a guilty criminal go free than to condemn an innocent man to death. Augustine's attacks of conscience partly explain his abhorrence of soothsayers, who offer to sacrifice animals to various spirits in order to assure Augustine's success in public rhetorical contests. John J. O'Meara observes that as a Manichee, Augustine would have objected to killing any living creature. Augustine may also have considered that the demons the soothsayer invoked were evil.
Augustine is not as adverse to astrology, which does not make appeals to evil spirits, but relies on an apparently rational observation of natural phenomena, namely the movements of the stars, in order to predict future events. Manichaeism also had its own kind of astrology, because its myths emphasized the roles of the sun and moon. Although he does not discount God's ability to intervene in the natural order in miraculous ways, Augustine deeply values rationality. He believes that natural order reflects God's divine order and that reasoned contemplation of the lower order of the physical world can lead the mind to the higher order of spiritual truth. Astrology's quasi-scientific elements may have appealed to this impulse in Augustine. However, looking back, he identifies astrology as contrary to Christian belief, because it denies individual freedom of choice. If the stars really control human behavior, human beings are not responsible for their own sins. This line of reasoning makes God the creator of sin, rather than making human beings responsible for their own sinful choices. Such an outcome both denies God's supreme goodness and devalues human moral responsibility. This point is worth remembering whenever you are tempted to accuse Augustine of devaluing the human will when he insists on the absolute human dependence upon God's grace for salvation.
A distinguished friend advises Augustine that astrology is fake; its so-called predictions of the future based on mere chance. This man had studied astrology in his youth, but gave it up once he concluded that it was simply bogus. The friend's appearance in the narrative parallels that of an ex-Manichee bishop at the end of Book 3, who advises Monica that Augustine will give up Manichaeism after he discovers for himself that it is false. Augustine presents here a repeated pattern of messages from God that he repeatedly ignores; the messages are correct, but he did not heed them at the time. Astrology reappears in Book 7.6, where Augustine finally gives it up completely. Augustine's nameless female companion appears for the first time in Book 4. Scholars usually refer to her as his concubine, but their relationship was more like that of a modern common-law marriage or domestic partnership. Although they were never officially married, they stayed together for 15 years, and Augustine himself says that he was faithful to her during that time. They had one child, a son, whose conception Augustine describes as unwanted; procreation was one of the worst sins possible for Manichee. Augustine does not say that he loved his concubine, and he describes their relationship as one based solely on sex — a selfish desire — rather than on the kind of friendship that would include unselfish, spiritual love. Nonetheless, his reaction at her forced departure in Book 6.15 indicates that he did care for her in some way, and his relationship with their son, Adeodatus, was affectionate, as described in Book 9.
Augustine's attitudes toward women in the Confessions are easily open to criticism by modern readers. It is tempting to simplify them into the woman-as-saint (Monica) and woman-as-temptress (concubine) pattern, but simplification is not entirely fair. Monica manages to emerge as a strong and morally complex character, and even the unnamed concubine shows a greater moral resolve than Augustine is able to when she vows to live in chastity after she is forced to leave Augustine. Feminine imagery is also common in Augustine's language for his relationship with God. An example appears in Book 4.1, where Augustine describes himself as a child seeking nourishment at the breast of a motherly God. As for Augustine's assertion that there was no true friendship between him and his concubine, it is worth remembering that in Augustine's society, educated women were rare. For a brilliant and highly educated man like Augustine, true companionship would have required an intellectual aspect that would have been difficult to find with most women of his time. Spiritual friendship of this kind would have been restricted to his close male friends, one of whom, Nebridius, makes his first appearance at the end of this section.